Two days before the July 18 signing deadline for the 2014 First-Year Player Draft, it remains unclear whether No. 1 overall pick Brady Aiken will come to terms with the Astros.

Houston made Aiken, a left-hander from Cathedral Catholic High (San Diego) who was the consensus top prospect in this year's Draft, the first choice June 5. Two days later, the two sides had agreed to a $6.5 million bonus, tying Jameson Taillon (Pirates, 2010) for the largest for a prep pitcher. Aiken flew to Houston on June 23 to take a physical and finalize a deal, but he left two days later without a contract.

CBSSports.com reported July 7 that Aiken's physical revealed concerns about his left elbow that put his deal on hold. Further complicating matters, Aiken's advisor is now accusing Houston of trying to manipulate its Draft pool to reduce Aiken's bonus and clear money to sign 21st-round pick Mac Marshall, a Parkview High (Lilburn, Ga.) left-hander who was considered a top-three-rounds talent.

Casey Close of Excel Sports Management, which represents big leaguers such as Derek Jeter and Clayton Kershaw, says that the Astros are mistreating Aiken and fifth-rounder Jacob Nix. A right-hander from Los Alamito (Calif.) High, Nix agreed to a $1.5 million bonus within two weeks of the Draft. But now he's caught in the crossfire, because if the Astros were to pay Nix $1.5 million and not sign Aiken, they would exceed their allotted bonus pool by more than 15 percent -- and forfeit their next two first-round picks as a penalty under the Draft rules.

Close says that Aiken is completely healthy, noting that his fastball touched 97 mph in his final start for Cathedral Catholic and that he has visited two orthopedists who found nothing wrong with his elbow. Close also says that Nix passed his physical, only to have the Astros subsequently tell him his offer was contingent on Aiken signing. Both Aiken and Nix have committed to UCLA.

"I'm not going to stand for it, the families aren't going to stand for it, and frankly, Major League Baseball shouldn't stand for it,'' Close said. "It's mind-boggling to me that other clubs wouldn't be appalled."

Houston general manager Jeff Luhnow has yet to confirm that Aiken or Nix ever agreed to terms, and he says that team policy won't allow him to comment on the specifics of ongoing negotiations. He does deny that the team is trying to use Aiken's physical as leverage against him.

"We've followed all of the rules," Luhnow said. "We've done nothing disingenuous throughout the whole process."

MLB Players Association executive director Tony Clark took note of the situation when speaking to the Baseball Writers' Association of America at the All-Star Game in Minneapolis on Tuesday. The No. 2 overall pick in the 1990 Draft by the Tigers, Clark said he was disappointed to see what was happening with Aiken and Nix.

"Our hope going forward is that what we think has happened didn't happen," Clark said. "You can rest assured that the manipulation we think happened in this case is going to lead us to have some conversations that are going to make sure the players receive the support they deserve as a result of the actions that we believe occurred with the Houston Astros."

The Astros have until 4 p.m. CT on Friday to complete a deal with Aiken and Nix. If Houston doesn't sign Aiken, it will receive the No. 2 overall choice in 2015 as compensation as long as it offers him at least 40 percent of his assigned pick value of $7,922,100. Close confirmed that the team has offered Aiken the minimum $3,168,840.

If Aiken attends UCLA, he wouldn't re-enter the Draft until 2017. He could be Draft-eligible in 2015 if he played at a junior college or in an independent professional league. Other options could include pursuing a grievance through the MLBPA or filing a lawsuit.

Since the Draft began in 1965, two No. 1 overall selections have not signed. In 1971, Peoria (Ill.) High catcher Danny Goodwin turned down the White Sox and went first overall again four years later, this time to the Twins, after attending Southern. Mount Vernon Nazarene (Ohio) right-hander Tim Belcher rebuffed the Twins in 1983 and signed with the Yankees as the top choice in the secondary phase of the 1984 January Draft.

Two recent parallels to Aiken's situation happened in the previous four Drafts. In 2010, Texas A&M right-hander Barret Loux agreed to a below-market $2 million bonus as the sixth overall choice by the D-backs, but he failed a post-Draft physical. Arizona decided to take the No. 7 pick in 2011 (which would become prized righty Archie Bradley) rather than sign Loux for a reduced amount. After negotiations between MLB and the MLBPA, Loux was declared a free agent and signed with the Rangers for $312,000.

Last year, St. Ignatius High (San Francisco) lefty Matt Krook agreed to terms with the Marlins as a supplemental first-round selection (35th overall) but failed his physical. Under the current Draft rules -- which didn't apply to Loux in the previous Collective Bargaining Agreement -- Miami offered him 40 percent of his assigned value and received the 36th pick in the 2014 Draft. Krook went on to attend Oregon, where he had Tommy John surgery this spring.

Multiple baseball sources contacted by MLB.com had a difficult time imagining that MLB would consent to granting Aiken free agency. If he did, estimates on the contract he might receive on the open market started at $25 million to $30 million. When four first-rounders became free agents after teams improperly tendered them contracts in 1996, Matt White ($10.2 million) and Travis Lee ($10 million) received five times the bonus of No. 1 overall pick Kris Benson ($2 million).

As of Tuesday evening, no further talks between Aiken and the Astros had been scheduled. Luhnow expressed hope that his club still would sign Aiken and Nix, though he admitted he didn't know if that would happen.

"We took Brady Aiken with the No. 1 pick in the Draft," Luhnow said. "That's not a pick you play games with. It's absurd that anyone would think that."

Jim Callis is a reporter for MLB.com and writes a blog, Callis' Corner. Follow @jimcallisMLB on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.